[NET]: Fix fib_rules compatibility breakage

Based upon a patch from Patrick McHardy.

The fib_rules netlink attribute policy introduced in 2.6.19 broke
userspace compatibilty. When specifying a rule with "from all"
or "to all", iproute adds a zero byte long netlink attribute,
but the policy requires all addresses to have a size equal to
sizeof(struct in_addr)/sizeof(struct in6_addr), resulting in a
validation error.

Check attribute length of FRA_SRC/FRA_DST in the generic framework
by letting the family specific rules implementation provide the
length of an address. Report an error if address length is non
zero but no address attribute is provided. Fix actual bug by
checking address length for non-zero instead of relying on
availability of attribute.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index bc3c26494c3d..d585ea9fa97d 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h
@@ -34,6 +34,7 @@ struct fib_rules_ops
         int                     family;
         struct list_head        list;
         int                     rule_size;
+        int                     addr_size;
 
         int                     (*action)(struct fib_rule *,
                                           struct flowi *, int,